Method for fabricating a semiconductor device having a trench exposing a sidewall of the contact plug aligned with the sidewall of the substrate

ABSTRACT

A method including forming an inter-layer insulation layer on a substrate, forming a plug material penetrating the inter-layer insulation layer and contacting a portion of the substrate, forming a contact plug by etching the plug material, forming a trench exposing a side wall of the contact plug by etching the substrate and the inter-layer insulation layer to be aligned with a side wall of the contact plug, forming a gate insulation layer on a surface of the trench and the exposed side wall of the contact plug, and forming a gate electrode partially filling the trench on the gate insulation layer. The method includes an inter-layer insulation layer formed on a substrate, a contact plug penetrating the inter-layer insulation layer and contacting a portion of the substrate, trenches extending in a line shape and aligned with side walls of the contact plug, and a plug spacer positioned between the trenches and surrounding the contact plug.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Korean Patent Application No.10-2020-0102401, filed on Aug. 14, 2020, which is herein incorporated byreference in its entirety.

BACKGROUND 1. Field

Various embodiments of the present disclosure relate to semiconductordevices and methods for manufacturing the same and, more specifically,to semiconductor devices with word lines and bit lines, and methods formanufacturing the same.

2. Description of the Related Art

As semiconductor devices become increasingly more highly integrated, thearea occupied by the word line and bit line contact plugs is shrinking.Accordingly, although various technologies have been proposed forpreventing a short defect which occurs between a word line and bit linecontact plug further improvements are needed. One such technologyemploys forming an oxide film between the word line and bit line contactplug.

SUMMARY

Embodiments of the present disclosure provide a semiconductor devicewith bit line contact plugs and gate insulation layers, and a method formanufacturing the semiconductor device.

According to an embodiment of the present disclosure, a method formanufacturing a semiconductor device comprises forming a contact hole ina substrate, filling the contact hole with a plug material, forming acontact plug by etching the plug material, forming a trench exposing aside wall of the contact plug by etching the substrate to be alignedwith a side wall of the contact plug, forming a gate insulation layer onthe exposed side wall of the contact plug and a surface of the trench,and forming a gate electrode on the gate insulation layer, the gateelectrode partially filling the trench.

According to another embodiment of the present disclosure, a method formanufacturing a semiconductor device comprises forming a contact hole ina substrate, forming a plug material filling the contact hole, forming abit line contact plug by etching the plug material, forming a gatetrench exposing a side wall of the bit line contact plug by etching thesubstrate to be self-aligned with a side wall of the bit line contactplug, forming a buried gate structure filling the gate trench, andforming a bit line on the bit line contact plug.

According to an embodiment of the present disclosure, a semiconductordevice comprises a substrate, a bit line contact plug positioned in thesubstrate, a trench positioned in the substrate and aligned with a sidewall of the bit line contact plug, a gate insulation layer formed on asurface of the trench and the side wall of the bit line contact plug,and a gate electrode partially filling the trench on the gate insulationlayer, wherein the gate insulation layer includes a first oxide.

According to another embodiment of the present disclosure, asemiconductor device comprises a substrate including an active area, afirst trench and a second trench spaced apart from each other andextending in the substrate, a bit line contact plug positioned betweenthe first trench and the second trench and formed in the substrate, afirst gate insulation layer formed on a surface of the first trench anda side wall of the bit line contact plug, a second gate insulation layerformed on a surface of the second trench and another side wall of thebit line contact plug, a first gate electrode partially filling thefirst trench, on the first gate insulation layer, and a second gateelectrode partially filling the second trench, on the second gateinsulation layer, wherein the first gate insulation layer includes anoxide of a side wall of the bit line contact plug, and wherein thesecond gate insulation layer includes an oxide of another side wall ofthe bit line contact plug.

These and other features and advantages of the present disclosure willbecome apparent to those with ordinary skill in the art of the inventionfrom the following figures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C, and 1D are views illustrating a semiconductor deviceaccording to an embodiment of the present disclosure;

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 2I, 2J, and 2K are viewsillustrating a method for manufacturing a semiconductor device accordingto an embodiment of the present disclosure;

FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, 3I, 3J, and 3K are cross-sectionalviews taken along line A-A′ and line B-B′ of FIGS. 2A to 2K;

FIGS. 4A, 4B, 4C, 4D, and 4E are views illustrating a method formanufacturing a semiconductor device according to an embodiment of thepresent disclosure;

FIG. 5 is a top view illustrating a semiconductor device according to anembodiment of the present disclosure;

FIGS. 6A, 6B, 6C, 6D, 6E, 6F, 6G, 6H, and 6I are cross-sectional viewsillustrating a semiconductor device according to an embodiment of thepresent disclosure;

FIG. 7 is a cross-sectional view illustrating a semiconductor deviceaccording to an embodiment of the present disclosure;

FIG. 8 is a cross-sectional view illustrating a semiconductor deviceaccording to an embodiment of the present disclosure;

FIGS. 9A and 9B are top views illustrating a semiconductor deviceaccording to an embodiment of the present disclosure; and

FIGS. 10A, 10B, 10C, and 10D are views illustrating a method formanufacturing a semiconductor device according to an embodiment of thepresent disclosure.

DETAILED DESCRIPTION

Example cross-sectional views, plan views, and block diagrams may beused herein to describe embodiments of the disclosure, and modificationsmay be made thereto according to, e.g., manufacturing techniques and/ortolerances. Thus, embodiments of the disclosure are not limited tospecific types as shown and illustrated herein but may rather encompasschanges or modifications resulting from fabricating processes. Forexample, the regions or areas shown in the drawings may be schematicallyshown, and their shapes shown are provided merely as examples, and arenot intended to limit the category or scope of the disclosure. Elementsshown in the drawings may be exaggerated in light of their thicknessesand intervals for illustration purposes. Well known components orelements irrelevant to the subject matter of the disclosure may beomitted from the description. The same or substantially the samereference denotations are used to refer to the same or substantially thesame elements throughout the specification and the drawings.

Hereinafter, embodiments of the disclosure are described in detail withreference to the accompanying drawings. For ease of description, thedescription focuses primarily on dynamic random-access memory (DRAM),but the disclosure is not limited thereto and may be applicable to othermemory or semiconductor devices.

FIGS. 1A, 1B, 1C, and 1D are views illustrating a semiconductor device100 according to an embodiment of the present disclosure. FIG. 1A is atop view of the semiconductor device 100. FIG. 1B shows cross-sectionalviews taken along line A-A′ and line B-B′ of FIG. 1A. FIG. 1C is anenlarged view of portion C of FIG. 1A. FIG. 1D is a perspective viewillustrating a plug spacer SP of the semiconductor device 100.

Referring to FIGS. 1A and 1B, an element isolation layer 103 may beformed on a substrate 101. The element isolation layer 103 may bepositioned in an isolation trench 102. The active areas 104 may bedefined by the element isolation layer 103.

The substrate 101 may include a material appropriate for semiconductorprocessing. The substrate 101 may include a semiconductor substrate. Thesubstrate 101 may be formed of a silicon-containing material. Thesubstrate 101 may include, for example, silicon, monocrystallinesilicon, polysilicon, amorphous silicon, silicon-germanium,monocrystalline silicon-germanium, polycrystalline silicon-germanium,carbon-doped silicon, a combination thereof or a multi-layer structurethereof. The substrate 101 may include other semiconductor materials,e.g., germanium. The substrate 101 may include a compound semiconductorsubstrate, e.g., a group-III to V semiconductor substrate, such as GaAs.The substrate 101 may include a silicon-on-insulator (SOI) substrate.

The element isolation layer 103 may be a shallow trench isolation (STI)area formed by trench etching. The element isolation layer 103 may beformed by filling a shallow trench, e.g., the isolation trench 102, withan insulation material. The element isolation layer 103 may include, forexample, a silicon oxide, a silicon nitride, or a combination thereof.Chemical vapor deposition (CVD) or other deposition processes may beused to fill the isolation trench 102 with the insulation material. Aplanarization process, such as chemical-mechanical polishing (CMP), maybe additionally used.

A source/drain area SD may be formed in the active area 104. A dopingprocess may be performed to form the source/drain areas SD. The dopingprocess may include, e.g., implantation or plasma doping (PLAD). Thesource/drain areas SD may be doped with a conductive impurity. Forexample, the conductive impurity may include phosphorus (P), arsenic(As), antimony (Sb), or boron (B). The bottom surface of thesource/drain areas SD may be positioned at a predetermined depth fromthe top surface of the active area 104. The source/drain areas SD maycorrespond to the source area and the drain area. The source/drain areasSD may have the same depth. The source/drain areas SD may each be anarea in which a bit line contact plug or a storage node contact plug isconnected.

An inter-layer insulation layer 105 may be formed on and may contact thesubstrate 101. The inter-layer insulation layer 105 may include aninsulation material. The inter-layer insulation layer 105 may include,for example, a silicon oxide, a silicon nitride, a low-k material, or acombination thereof. The inter-layer insulation layer 105 may includetetraethyl orthosilicate (TEOS). The inter-layer insulation layer 105may include one or more layers. The inter-layer insulation layer 105 mayinclude one or more layers formed of different materials. According toan embodiment, the inter-layer insulation layer 105 may include twolayers. According to an embodiment, the inter-layer insulation layer 105may include a layer formed of silicon oxide and a layer formed ofsilicon nitride.

A trench T may be formed in the substrate 101. The trench T may bereferred to as a ‘gate trench.’ The trench T may include a first trenchT1 and a second trench T2 parallel with the first trench T1. The firsttrench T1 and the second trench T2 may be spaced apart from each otherand extend along a direction. The trench T may have a line shape thatcrosses the active area 104 and the element isolation layer 103. A sidewall of the trench T may abut the source/drain area SD. The bottomsurface of the trench T may be at a lower level than the bottom surfacesof the source/drain areas SD. The bottom surface of the trench T may beat a higher level than the bottom surface of the element isolation layer103. The trench T may include an upper area provided by etching theinter-layer insulation layer 105 and a lower area provided by etchingthe substrate 101. The lower area of the trench T may have a largerdepth than the upper area of the trench T.

A contact plug 106 may be formed between the trenches T. The contactplug 106 may be formed between the first trench T and the second trenchT2. The contact plug 106 may penetrate the inter-layer insulation layer105. The contact plug 106 may be formed in the substrate 101. Thecontact plug 106 may pass through the inter-layer insulation layer 105and extend inside the substrate 101. The contact plug 106 may bereferred to as a ‘buried plug.’ The contact plug 106 may include a lowerportion extending to the inside of the substrate 101 and an upperportion penetrating the inter-layer insulation layer 105. The depth ofthe lower portion of the contact plug 106 may be larger than the depthof the upper portion. That is, the depth of the portion extending to theinside of the substrate 101 in the contact plug 106 may be larger thanthe depth of the portion penetrating the inter-layer insulation layer105. The contact plug 106 may be buried in the substrate 101.

The top view of the contact plug 106 may be shaped as an oval brokenbetween surfaces facing each other. The top view of the contact plug 106may be shaped as a circle broken between surfaces facing each other. Thetop view of the contact plug 106 may have a rectangular shape. Thetrenches T may be self-aligned with the side surfaces of the contactplug 106. The trenches T may include a first trench T positioned on oneside surface of the contact plug 106. The trenches T may include asecond trench T positioned on the opposite side surface of the contactplug 106. Both of the side walls of the contact plug 106 may contact thefirst trench T and the second trench T2. The bottom surface of thetrench T may be positioned deeper than the bottom surface of the contactplug 106. A cross section of the contact plug 106 may have the samewidth at its top and bottom portions. A cross section of the contactplug 106 may have a larger width at the top portion than at the bottomportion. A cross section of the contact plug 106 may have a verticalshape. A cross section of the contact plug 106 may have a sloped shape.

The contact plug 106 may include a semiconductor material. The contactplug 106 may include a silicon-containing material. The contact plug 106may include, for example, polysilicon. The polysilicon may be doped withan impurity. According to an embodiment, the contact plug 106 may beformed by selective epitaxial growth (SEG). For example, the contactplug 106 may include SEG silicon phosphorus (SiP). A void-free contactplug 106 may be formed by selective epitaxial growth (SEG).

A plug spacer SP may be formed to surround the outer wall of the contactplug 106. The plug spacer SP may not overlap the trench T. The top viewof the plug spacer SP may have a discontinuous ring shape. A crosssection of the plug spacer SP may have a sloped shape. The plug spacerSP may discontinuously surround the lower outer wall of the contact plug106. The plug spacer SP may be positioned between trenches T. The plugspacer SP may include an insulation material. The plug spacer SP mayinclude a nitrogen-containing material. The plug spacer SP may include,for example, silicon oxide, silicon nitride, silicon oxynitride, or acombination thereof. According to an embodiment, the plug spacer SP maybe formed of silicon nitride. The plug spacer SP may be formed, forexample, by chemical vapor deposition (CVD) or atomic layer deposition(ALD). The plug spacer SP may be selectively grown by an atomic layerdeposition (ALD) or low-pressure chemical vapor deposition (LPCVD)process using dichlorosilane (SiH₂Cl₂) and ammonia (NH₃) as reactivegases.

A gate structure BG may be formed in the trench T. The gate structure BGmay include a gate insulation layer 107, a gate electrode 108, and agate capping layer 109. The gate structure BG may extend in the form ofa line. The gate structure BG may be referred to as a ‘buried gatestructure.’

The gate insulation layer 107 may be formed on and may contact thesurface and side walls of the trench T. The gate insulation layer 107may cover the surface and side walls of the trench T. The gateinsulation layer 107 may vertically and continuously extend from thebottom surface of the trench T to the side walls of the contact plug106. The gate insulation layer 107 may be formed by depositing an oxidefilm or nitride film. The gate insulation layer 107 may be formed by adeposition method, such as chemical vapor deposition (CVD) or atomiclayer deposition (ALD). The gate insulation layer 107 may be formed byoxidation as well. The gate insulation layer 107 may be formed bythermal oxidation. According to an embodiment, the gate insulation layer107 may be formed by oxidating the bottom surface and side walls of thetrench T.

The gate insulation layer 107 may include a first oxide 107A, a secondoxide 107B, and a third oxide 107C. The first oxide 107A may include anoxide of a side wall of the contact plug 106. The first oxide 107A maybe formed by oxidating an exposed side wall of the contact plug 106. Thesecond oxide 107B may include an oxide of an exposed surface of thesubstrate 101. The second oxide 107B may be formed by oxidating theexposed surface of the substrate 101. The exposed surface of thesubstrate 101 may be formed by the trench T. The third oxide 107C mayinclude an oxide of an exposed surface of the inter-layer insulationlayer 105. The third oxide 107C may be formed by oxidating the exposedsurface of the inter-layer insulation layer 105. The exposed surface ofthe inter-layer insulation layer 105 may be formed by the trench T. Thesecond oxide 107B may extend from the first oxide 107A. The second oxide107B may extend from the third oxide 107C.

The gate insulation layer 107 may include, for example, silicon oxide,silicon nitride, silicon oxynitride, a high-k material, or a combinationthereof. The high-k material may include a material having a largerdielectric constant than the dielectric constant of silicon oxide. Thehigh-k material may include at least one metallic element. The high-kmaterial may include a hafnium-containing material. Thehafnium-containing material may include hafnium oxide, hafnium siliconoxide, hafnium silicon oxynitride, or a combination thereof. Accordingto an embodiment, the high-k material may include lanthanum oxide,lanthanum aluminum oxide, zirconium oxide, zirconium silicon oxide,zirconium silicon oxynitride, aluminum oxide, or a combination thereof.As the high-k material, other known high-k materials may be optionallyused. The first oxide 107A, the second oxide 107B, and the third oxide107C may include the same material. The first oxide 107A, the secondoxide 107B, and the third oxide 107C may include, for example, siliconoxide.

The gate electrode 108 may be formed on and may contact the gateinsulation layer 107. The gate electrode 108 may partially fill thetrench T. To form the gate electrode 108, a recess process may beperformed. Accordingly, the gate electrode 108 may be referred to as a‘buried gate electrode’ or ‘buried word line.’ The top surface of thegate electrode 108 may be at a lower level than the bottom surface ofthe contact plug 106. The top surface of the gate electrode 108 may beat the same level as the bottom surface of the contact plug 106.

The gate electrode 108 may include a metal, metal nitride, or acombination thereof. For example, the gate electrode 108 may be formedof titanium nitride (TiN), tungsten (W), or titanium nitride/tungsten(TiN/W). The titanium nitride/tungsten (TiN/W) may have a structurewhich results from conformally forming titanium nitride and thenpartially filling the trench T with tungsten. The gate electrode 108 mayinclude titanium nitride. The gate electrode 108 may include atungsten-containing material that includes tungsten as a main element.

The gate capping layer 109 may be formed on and may contact the gateelectrode 108. The gate capping layer 109 may fill the rest of thetrench T. The gate capping layer 109 may neighbor the contact plug 106,with the gate insulation layer 107 therebetween separating the two. Thatis, the gate insulation layer 107 may extend to be positioned betweenthe gate capping layer 109 and the contact plug 106 to electricallyisolate the two. The top surface of the gate capping layer 109 may be atthe same level as the top surface of the inter-layer insulation layer105. The gate capping layer 109 includes an insulation material. Thegate capping layer 109 may include, for example, silicon nitride.According to an embodiment, the gate capping layer 109 may include, forexample, silicon oxide. According to an embodiment, the gate cappinglayer 109 may have a multi-layer nitride-oxide-nitride (NON) structure.

Referring to FIG. 1C, the contact plug 106 may include a first sidesurface S1 and a second side surface S2 positioned opposite the firstside surface S1. The top view of the contact plug 106 may include athird side surface S3 and a fourth side surface S4 positioned oppositethe third side surface S3. The first and second side surfaces S1 and S2may cross the third and fourth side surfaces S3 and S4.

The first side surface S1 may be parallel with the second side surfaceS2. The first side surface S1 and the second side surface S2 may have astraight shape. The first side surface S1 and the second side surface S2may have a straight profile. The first side surface S1 and the secondside surface S2 may not directly contact the plug spacer SP. The firstside surface S1 and the second side surface S2 may directly contact thegate insulation layer 107.

The third side surface S3 and the fourth side surface S4 may face eachother. The third side surface S3 and the fourth side surface S4 may havea curved or round shape. The third side surface S3 and the fourth sidesurface S4 may have a curved or round profile. The third side surface S3and the fourth side surface S4 may directly contact the plug spacer SP.The third side surface S3 and the fourth side surface S4 may notdirectly contact the gate insulation layer 107.

The top view of the contact plug 106 may have various shapes, including,for example, a circle, oval, or rectangle. The width WX in the Xdirection of the contact plug 106 may be the same as the width WY in theY direction. The width WX in the X direction of the contact plug 106 maybe smaller than the width WY in the Y direction. The width WX in the Xdirection of the contact plug 106 may be larger than the width WY in theY direction.

Referring to FIG. 1D, the plug spacer SP may include a pair of sidewalls facing each other. The plug spacer SP may have a curved or roundshape. The plug spacer SP may include parallel cross sections.

The top view of the cross section in the D1 direction of the plug spacerSP may have a discontinuous ring shape. The top view of the crosssection in the D1 direction of the plug spacer SP may have curved orround shapes facing each other. The interval between a pair of sidewalls facing each other of the plug spacer SP may decrease from theupper level to the lower level. A cross section in the D2 direction ofthe plug spacer SP may have a sloped shape. A cross section in the D2direction of the plug spacer SP may have a straight shape.

According to the above-described embodiment, the process difficulty informing the contact plug 106 may be reduced by forming the contact plug106 earlier than the gate structure BG. Thus, a stable structure may beformed. Further, a short defect between the contact plug 106 and thegate electrode 108 may be mitigated by forming the gate insulation layer107 on the side wall of the contact plug 106.

FIGS. 2A to 2K and FIGS. 3A to 3K are views illustrating a method formanufacturing a semiconductor device according to an embodiment of thepresent disclosure. FIGS. 2A to 2K are top views of a semiconductordevice. FIGS. 3A to 3K are cross-sectional views taken along line A-A′and B-B′ of FIGS. 2A to 2K.

Referring to FIGS. 2A and 3A, a substrate 11 is prepared. The substrate11 may include a material appropriate for semiconductor processing. Thesubstrate 11 may include a semiconductor substrate. The substrate 11 maybe formed of a silicon-containing material. The substrate 11 mayinclude, for example, silicon, monocrystalline silicon, polysilicon,amorphous silicon, silicon-germanium, monocrystalline silicon-germanium,polycrystalline silicon-germanium, carbon-doped silicon, a combinationthereof or a multi-layer structure thereof. The substrate 11 may includeother semiconductor material, e.g., germanium. The substrate 11 mayinclude a compound semiconductor substrate, e.g., a group-III to Vsemiconductor substrate, such as GaAs. In an embodiment, the substrate11 may include a silicon-on-insulator (SOI) substrate.

An element isolation layer 13 and active areas 14 may be formed in thesubstrate 11. The active areas 14 may be defined by the elementisolation layer 13. The element isolation layer 13 may be a shallowtrench isolation (STI) area formed by trench etching. The elementisolation layer 13 may be formed by filling a shallow trench, e.g., theisolation trench 12, with an insulation material. The element isolationlayer 13 may include, for example, a silicon oxide, a silicon nitride,or a combination thereof. Chemical vapor deposition (CVD) or otherdeposition processes may be used to fill the isolation trench 12 withthe insulation material. A planarization process, such aschemical-mechanical polishing (CMP), may be additionally used.

Source/drain areas SD may be formed in the active area 14. A dopingprocess may be performed to form the source/drain areas SD. The dopingprocess may include, e.g., implantation or plasma doping (PLAD). Thesource/drain areas SD may be doped with a conductive impurity. Forexample, the conductive impurity may include phosphorus (P), arsenic(As), antimony (Sb), or boron (B). The bottom surface of each of thesource/drain areas SD may be positioned at a predetermined depth fromthe top surface of the active area 14. The source/drain areas SD maycorrespond to the source area and the drain area. The source/drain areasSD may have the same depth. The source/drain areas SD may each be anarea in which a bit line contact plug or a storage node contact plug isconnected.

An inter-layer insulation layer 15 may be formed on and may contact thesubstrate 11. The inter-layer insulation layer 15 may include aninsulation material. The inter-layer insulation layer 15 may include,for example, a silicon oxide, a silicon nitride, a low-k material, or acombination thereof. In an embodiment, the inter-layer insulation layer15 may include tetraethyl orthosilicate (TEOS). The inter-layerinsulation layer 15 may include one or more layers. The inter-layerinsulation layer 15 may include one or more layers formed of differentmaterials. According to an embodiment, the inter-layer insulation layer15 may include two layers. According to an embodiment, the inter-layerinsulation layer 15 may include a layer formed of silicon oxide and alayer formed of silicon nitride.

Referring to FIGS. 2B and 3B, a contact hole mask 16 may be formed onand may contact the inter-layer insulation layer 15. The contact holemask 16 may include a photoresist pattern.

A contact hole 17 may be formed by etching the inter-layer insulationlayer 15 using the contact hole mask 16 as an etch mask. From a topview, the contact hole 17 may be shaped as a circle or oval. The contacthole 17 may be formed to penetrate the inter-layer insulation layer 15.A step of recessing the exposed surface of the substrate 11 may beincluded. The contact hole 17 may be formed in the substrate 11. Uponetching the inter-layer insulation layer 15 using the contact hole mask16 as an etch mask, a portion of the substrate 11 may be etched togetherwith the inter-layer insulation layer 105. Accordingly, a portion of thesubstrate 11 may be exposed through the contact hole 17. The bottomsurface of the contact hole 17 may be positioned at a lower level thanthe top surface of the substrate 11. The bottom surface of the contacthole 17 may be positioned at a higher level than the bottom surface ofthe source/drain area SD.

Referring to FIGS. 2C and 3C, a preliminary spacer layer 18A′ may beformed to cover the inter-layer insulation layer 15 and the contact hole17. The preliminary spacer layer 18A′ may include an insulationmaterial. The preliminary spacer layer 18A′ may include anitrogen-containing material. The preliminary spacer layer 18A′ mayinclude, for example, silicon oxide, silicon nitride, siliconoxynitride, or a combination thereof. According to an embodiment, thepreliminary spacer layer 18A′ may be formed of silicon nitride.

The preliminary spacer layer 18A′ may be formed, for example, bychemical vapor deposition (CVD) or atomic layer deposition (ALD). Thepreliminary spacer layer 18A′ may be selectively grown by an atomiclayer deposition (ALD) or low-pressure chemical vapor deposition (LPCVD)process using dichlorosilane (SiH₂Cl₂) and ammonia (NH₃) as reactivegases.

Referring to FIGS. 2D and 3D, a preliminary spacer 18A may be formed byetching the preliminary spacer layer 18A′. As the preliminary spacer 18Ais formed, a portion of the substrate 11 may be exposed. As thepreliminary spacer 18A is formed, the bottom surface of the contact hole17 may be exposed. The surface of the substrate 11 which is exposedinside the contact hole 17, may be further expanded using thepreliminary spacer 18A. The substrate 11 exposed inside the contact hole17 may be further recessed using the preliminary spacer 18A. The surfaceof the substrate 11, exposed inside the contact hole 17, may be furtheretched using the preliminary spacer 18A. Accordingly, a recessed contacthole 17R may be formed.

The recessed contact hole 17R may penetrate the inter-layer insulationlayer 15. The bottom surface of the recessed contact hole 17R may beformed in the substrate 11. The recessed contact hole 17R may penetratethe inter-layer insulation layer 105 and be formed in the substrate 11.

As the preliminary spacer 18A is formed, the top surface of theinter-layer insulation layer 15 may be exposed. The preliminary spacer18A may cover the side wall of the recessed contact hole 17R. Thepreliminary spacer 18A may be shaped to surround the side wall of therecessed contact hole 17R. From a top view, the preliminary spacer 18Amay have a ring shape. The circumference of the preliminary spacer 18Amay narrower from the top of the preliminary spacer 18A to the bottom. Across section of the preliminary spacer 18A may have a sloped shape.

Referring to FIGS. 2E and 3E, a plug material 19A may be formed in thecontact hole 17R. The plug material 19A may fill the contact hole 17R.To form the plug material 19A, a plug material layer 19A′ may be formedto cover the inter-layer insulation layer 15. There may be included theprocess of planarizing the plug material layer 19A′ to expose the topsurface of the inter-layer insulation layer 15. Accordingly, the topsurface of the plug material 19A may be exposed. The top surface of theplug material 19A may be at the same level as the top surface of theinter-layer insulation layer 15. The plug material 19A may penetrate theinter-layer insulation layer 15 and contact a portion of the substrate11.

The plug material 19A may include a semiconductor material. The plugmaterial 19A may include a conductive material. The plug material 19Amay include a silicon-containing material. The plug material 19A mayinclude, for example, polysilicon. The polysilicon may be doped with animpurity. According to an embodiment, the plug material 19A may beformed by selective epitaxial growth (SEG). For example, the plugmaterial 19A may include SEG silicon phosphorus (SiP). As such, avoid-free plug material 19A may be formed by SEG.

Referring to FIGS. 2F and 3F, a trench hard mask layer 20A may be formedon and may directly contact the inter-layer insulation layer 15 and theplug material 19A. The trench hard mask layer 20A may be formed todefine at least one or more openings in the inter-layer insulation layer15. The trench hard mask layer 20A may have a multi-layer structure. Thetrench hard mask layer 20A may include one or more layers. The height ofthe trench hard mask layer 20A may be larger than the height of theinter-layer insulation layer 15. The trench hard mask layer 20A mayinclude, for example, silicon oxide, silicon nitride, siliconoxynitride, or a combination thereof. According to an embodiment, thetrench hard mask layer 20A may be formed of silicon nitride.

The trench hard mask layer 20A may be formed, for example, by chemicalvapor deposition (CVD), physical vapor deposition (PVD), or atomic layerdeposition (ALD). To increase the deposition effect, the trench hardmask layer 20A may use a plasma. For example, the trench hard mask layer20A may be formed by plasma enhanced CVD (PECVD) or plasma enhanced ALD(PEALD).

Referring to FIGS. 2G and 3G, a trench mask pattern 20M may be formed onand may contact the trench hard mask layer 20A. The trench mask pattern20M may be formed by a known photolithography process. The trench maskpattern 20M may include a hard mask pattern patterned by a photoresistpattern. The trench mask pattern 20M may include a line-type mask.

The trench hard mask layer 20A may be etched using the trench maskpattern 20M as an etch mask. A trench hard mask 20 may be formed byetching the trench hard mask layer 20A. A portion of the inter-layerinsulation layer 15 and a portion of the substrate 11 may be etchedusing the trench hard mask 20 as an etch mask. A trench 21 may be formedby etching a portion of the inter-layer insulation layer 15 and aportion of the substrate 11. The trench 21 may be referred to as a ‘gatetrench.’ The trench 21 may have a line shape that crosses the activearea 14 and the element isolation layer 13. There may be formed aplurality of trenches 21 spaced apart from each other.

The trenches 21 may be self-aligned with the side surfaces of thecontact plug 19B. The trenches 21 may be self-aligned with the exposedside walls of the contact plug 19B. The side wall of the contact plug19B may abut the trench 21. As the trench 21 is formed, a portion of theside wall of the contact plug 19B may be exposed.

The bottom surface of the trench 21 may be at a lower level than thebottom surface of the contact plug 19B. The bottom surface of the trench21 may be at a higher level than the bottom surface of the elementisolation layer 13. The side wall of the trench 21 may abut thesource/drain area SD. The bottom surface of the source/drain area SD maybe higher than the bottom surface of the trench 21. The trench 21 mayinclude an upper area provided by etching the inter-layer insulationlayer 15 and a lower area provided by etching the substrate 11, and thelower area may have a larger depth than the upper area. The trench 21may have a depth sufficient to increase the average cross-sectional areaof the subsequent gate electrode. Accordingly, the resistance of thegate electrode may be reduced. Although not shown, a portion of theelement isolation layer 13 may be recessed, allowing the top portion ofthe active area 14 under the trench 21 to protrude. For example, theelement isolation layer 13 under the trench 21 may be optionallyrecessed. Accordingly, a fin region may be formed under the trench 21.The fin region may be part of a channel area.

As the trench 21 is formed, a portion of the plug material 19A may beremoved (R). The trench 21 may etch both the side walls of the plugmaterial 19A. As the plug material 19A is etched, the contact plug 19Bmay be formed. That is, the contact plug 19B may be formedsimultaneously with the formation of the trench 21. The contact plug 19Bmay be formed between trenches 21. The contact plug 19B may penetratethe inter-layer insulation layer 15. The contact plug 19B may be formedin the substrate 11. The contact plug 19B may pass through theinter-layer insulation layer 15 and extend to the inside of thesubstrate 11. The contact plug 19B may be referred to as a ‘buriedplug.’ The contact plug 19B may include a lower portion extending to theinside of the substrate 11 and an upper portion penetrating theinter-layer insulation layer 15. The lower portion of the contact plug19B may have a larger depth than the upper portion thereof. Namely, thedepth of the portion extending to the inside of the substrate 11 in thecontact plug 19B may be larger than the depth of the portion penetratingthe inter-layer insulation layer 15. The contact plug 19B may be buriedin the substrate 11.

From a top view, the contact plug 19B may be shaped as an oval or circlebroken between two facing surfaces. The width WT of the top portion ofthe contact plug 19B may be identical to the width WB of the bottomportion. A cross section of the contact plug 19B may have a verticalshape. A cross section of the contact plug 19B may have a sloped shape.The exposed side wall of the contact plug 19B may include a straightprofile. The non-exposed side wall of the contact plug 19B may include acurved or round profile.

As the trench 21 is formed, a portion of the preliminary spacer 18A maybe removed (R). The trench 21 may etch a portion of the preliminaryspacer 18A. As the preliminary spacer 18A is etched, the plug spacer 18may be formed. The plug spacer 18 may be formed as the preliminaryspacer 18A is cut. The plug spacer 18 may cover the non-exposed sidewall of the contact plug 19B. The plug spacer 18 may surround a portionof the outer wall of the contact plug 19B. The plug spacer 18 may notoverlap the trench 21. The top view of the plug spacer 18 may have adiscontinuous ring shape. The top view of the plug spacer 18 may beshaped as curved or round shapes facing each other. A cross section ofthe plug spacer 18 may have a sloped shape. The plug spacer 18 maydiscontinuously surround the lower outer wall of the contact plug 19B.The plug spacer 18 may be positioned between trenches 21.

Referring to FIGS. 2H and 3H, a preliminary gate insulation layer 22Amay be formed on and in direct contact with the bottom surface and sidewalls of the trench 21. The preliminary gate insulation layer 22A may beformed on and in direct contact with the exposed side wall of thecontact plug 19B. The preliminary gate insulation layer 22A may beformed on and in direct contact with the surface of the trench 21.Before forming the preliminary gate insulation layer 22A, etch damage tothe surface of the trench 21 may be cured. For example, a sacrificialoxide may be formed by thermal oxidation and may then be removed.

The preliminary gate insulation layer 22A may be formed by depositing anoxide film or a nitride film. The preliminary gate insulation layer 22Amay be formed on and may directly contact the bottom surface and sidewall of the trench 21. The preliminary gate insulation layer 22A may beformed on and may directly contact the side wall of the inter-layerinsulation layer 15, exposed by the trench 21. The preliminary gateinsulation layer 22A may be formed on and may directly contact the sidewall of the contact plug 19B, exposed by the trench 21. The preliminarygate insulation layer 22A may be formed on and may directly contact thetop surface and side wall of the trench hard mask 20, exposed by thetrench 21. Accordingly, the preliminary gate insulation layer 22A maycover the trench 21, inter-layer insulation layer 15, contact plug 19B,and trench hard mask 20. The preliminary gate insulation layer 22A maybe formed by a deposition method, such as, for example, chemical vapordeposition (CVD) or atomic layer deposition (ALD).

According to an embodiment, the preliminary gate insulation layer 22Amay be formed by oxidation. For example, the preliminary gate insulationlayer 22A may be formed by thermal oxidation. According to anembodiment, the preliminary gate insulation layer 22A may be formed byoxidating the side walls of the contact plug 19B and the surface of thetrench 21. The preliminary gate insulation layer 22A may be formed byoxidating the substrate 11 exposed by the trench 21. The preliminarygate insulation layer 22A may be formed by oxidating the side walls ofthe contact plug 19B, exposed by the trench 21. The preliminary gateinsulation layer 22A may be formed by oxidating the side wall of theinter-layer insulation layer 15, exposed by the trench 21. Thepreliminary gate insulation layer 22A may be formed by oxidating the topsurface and side wall of the trench hard mask 20, exposed by the trench21. The oxide film formed on the top surface and the side wall of thetrench hard mask 20, exposed by the trench 21, may be smaller inthickness than the oxide film formed on the side wall of the inter-layerinsulation layer 15. No oxide film may be formed on the top surface andside wall of the trench hard mask 20 exposed by the trench 21.Accordingly, the preliminary gate insulation layer 22A may cover thetrench 21, the side wall of the inter-layer insulation layer 15, and theside wall of the contact plug 19B.

The preliminary gate insulation layer 22A may include, for example,silicon oxide, silicon nitride, silicon oxynitride, a high-k material,or a combination thereof. The high-k material may include a materialhaving a larger dielectric constant than the dielectric constant ofsilicon oxide. The high-k material may include at least one metallicelement. The high-k material may include a hafnium-containing material.The hafnium-containing material may include hafnium oxide, hafniumsilicon oxide, hafnium silicon oxynitride, or a combination thereof.According to an embodiment, the high-k material may include lanthanumoxide, lanthanum aluminum oxide, zirconium oxide, zirconium siliconoxide, zirconium silicon oxynitride, aluminum oxide, or a combinationthereof. As the high-k material, other known high-k materials may beoptionally used.

Referring to FIGS. 2I and 3I, a gate electrode 23 may be formed on andmay directly contact the preliminary gate insulation layer 22A. To formthe gate electrode 23, a conductive layer (not shown) may be formed tofill the trench 21, and then, a recessing process may be performed. Asthe recessing process, an etchback process may be performed, or achemical mechanical polishing (CMP) process and an etchback process maysequentially be performed. The gate electrode 23 may partially fill thetrench 21. Accordingly, the gate electrode 23 may be referred to as a‘buried gate electrode’ or ‘buried word line.’ The top surface of thegate electrode 23 may be at a lower level than the bottom surface of thecontact plug 19B. The top surface of the gate electrode 23 may be at thesame level as the bottom surface of the contact plug 19B.

The gate electrode 23 may include a metal, metal nitride, or acombination thereof. For example, the gate electrode 23 may be formed oftitanium nitride (TiN), tungsten (W), or titanium nitride/tungsten(TiN/W). The titanium nitride/tungsten (TiN/W) may have a structurewhich results from conformally forming titanium nitride and thenpartially filling the trench 21 with tungsten. As the gate electrode 23,titanium nitride alone may be used, which may be referred to as a “TiNOnly” structure of gate electrode 23. The gate electrode 23 may includea tungsten-containing material that includes tungsten as a main element.

Subsequently, a doping process may be optionally performed. The dopingprocess may include, e.g., implantation or plasma doping (PLAD).

Referring to FIGS. 2J and 3J, a preliminary gate capping layer 24A maybe formed on and may directly contact the gate electrode 23. The rest ofthe trench 21 may be filled with the preliminary gate capping layer 24A.The preliminary gate capping layer 24A may cover the preliminary gateinsulation layer 22A.

The preliminary gate capping layer 24A includes an insulation material.The preliminary gate capping layer 24A may include, for example, siliconnitride. According to an embodiment, the preliminary gate capping layer24A may include, for example, silicon oxide. The preliminary gatecapping layer 24A may have a multi-layer structure. The preliminary gatecapping layer 24A may include one or more layers. The preliminary gatecapping layer 24A may have a multi-layer nitride-oxide-nitride (NON)structure.

Referring to FIGS. 2K and 3K, a gate capping layer 24 may be formed inthe trench 21. The top surface of the gate capping layer 24 may be atthe same level as the top surface of the inter-layer insulation layer15. To that end, chemical mechanical polishing (CMP) may be performedupon forming the gate capping layer 24. The gate capping layer 24 may beformed via an etching process using a separate mask. During this course,the trench hard mask 20, preliminary gate insulation layer 22A, andpreliminary gate capping layer 24A, positioned on the top surface of thecontact plug 19B and the inter-layer insulation layer 15 may be removed.Accordingly, the top surface of the inter-layer insulation layer 15 maybe exposed. As a portion of the preliminary gate insulation layer 22A isremoved, a gate insulation layer 22 may be formed inside the trench 21.

The gate insulation layer 22 may be formed on and may contact thesurface of the trench 21, the side wall of the contact plug 19B, and theside wall of the inter-layer insulation layer 15. The gate insulationlayer 22 may include a first oxide which is the oxide of the side wallof the contact plug 19B. The gate insulation layer 22 may include asecond oxide which is the oxide of the surface of the substrate 11exposed by the trench 21. The gate insulation layer 22 may include athird oxide which is the oxide of the side wall of the contact plug 19Bexposed by the trench 21. The first oxide, the second oxide, and thethird oxide may be continuous. The first oxide, the second oxide, andthe third oxide may include the same material. The first oxide, thesecond oxide, and the third oxide may include, for example, siliconoxide. The gate insulation layer 22 may extend to be positioned betweenthe gate capping layer 24 and the contact plug 19B.

The gate insulation layer 22, the gate electrode 23, and the gatecapping layer 24 may form a gate structure 25. The gate structure 25 maybe formed in the trench 21. The gate structure 25 may extend in a lineshape. The contact plug 19B may be positioned between gate structures25. The gate structure 25 may be referred to as a ‘buried gatestructure.’

According to the above-described embodiment, the process difficulty informing the contact plug 19B may be reduced by forming the contact plug19B earlier than the gate electrode 23. Further, a short defect betweenthe contact plug 19B and the gate electrode 23 may be mitigated byforming the gate insulation layer 22 on the side wall of the contactplug 19B.

FIGS. 4A to 4E are views illustrating a semiconductor device accordingto an embodiment of the present disclosure. FIGS. 4A to 4D arecross-sectional views illustrating a method for manufacturing asemiconductor device according to an embodiment of the presentdisclosure. FIG. 4E is a perspective view illustrating a plug spacer18′.

First, the preliminary spacer 18A and the plug material 19A may beformed in the contact hole 17 by the method illustrated in FIGS. 2A to2F and FIGS. 3A to 3F. In FIGS. 4A to 4D, the same reference numbers areused to denote the same elements as those in FIGS. 3A to 3F. Detaileddescription of duplicate elements may be omitted.

Referring to FIGS. 4A to 4D, a semiconductor device 200 may be similarto the semiconductor device 100 of FIG. 1B.

Referring to FIG. 4A, a trench hard mask 30 may be formed on and maycontact the substrate 11. A trench mask pattern 30M may be formed on andmay contact the trench hard mask 30. The trench mask pattern 30M may beformed by a known photolithography process. The trench mask pattern 30Mmay include a hard mask pattern patterned by a photoresist pattern.

A trench hard mask layer (not shown) may be etched using the trench maskpattern 30M as an etch mask. A trench hard mask 30 may be formed byetching the trench hard mask layer (not shown).

The trench hard mask 30 may have a multi-layer structure. The trenchhard mask 30 may include one or more layers. The height of the trenchhard mask 30 may be larger than the height of the inter-layer insulationlayer 15. The trench hard mask 30 may include, for example, siliconoxide, silicon nitride, silicon oxynitride, or a combination thereof.According to an embodiment, the trench hard mask 30 may be formed ofsilicon nitride. The trench hard mask 30 may be formed by the samemethod given for the trench hard mask 20 of FIG. 3G.

A trench 31 may be formed using the trench hard mask 30 as an etch mask.The trench 31 may be referred to as a ‘gate trench.’ Part of the plugmaterial 19A and inter-layer insulation layer 15 and the substrate 11may be etched using the trench hard mask 30 as an etch mask. Thus, thetrench 31 may be formed.

As the trench 31 is formed, a portion of the substrate 11 may beexposed. The top view of FIG. 4A may be the same as FIG. 2G. The trench31 may have a line shape that crosses the active area 14 and the elementisolation layer 13. The bottom surface of the trench 31 may be at ahigher level than the bottom surface of the element isolation layer 13.The trench 31 may have a smaller depth than the element isolation layer13. The side wall of the trench 31 may abut the source/drain area SD.The bottom surface of the source/drain area SD may be higher than thebottom surface of the trench 31. The trench 31 may include an upper areaprovided by etching the inter-layer insulation layer 15 and a lower areaprovided by etching the substrate 11, and the lower area may have alarger depth than the upper area. The trench 31 may have a depthsufficient to increase the average cross-sectional area of thesubsequent gate electrode. Accordingly, the resistance of the gate maybe reduced. A fin region may be formed under the trench 31.

As the trench 31 is formed, a portion of the plug material 19A may beremoved (R′). As the trench 31 is formed, both the side walls of theplug material 19A may be etched. The contact plug 19B′ may be formed byetching the plug material 19A. That is, the contact plug 19B′ may beformed simultaneously with the formation of the trench 31.

The contact plug 106 may be formed between trenches 31. The contact plug19B′ may penetrate the inter-layer insulation layer 15. The contact plug19B′ may be formed in the substrate 11. The contact plug 19B′ may passthrough the inter-layer insulation layer 15 and extend to the inside ofthe substrate 11. The contact plug 19B′ may be referred to as a ‘buriedplug.’ The contact plug 19B′ may include a lower portion extending tothe inside of the substrate 11 and an upper portion penetrating theinter-layer insulation layer 15. The lower portion of the contact plug19B′ may have a larger depth than the upper portion thereof. Namely, thedepth of the portion extending to the inside of the substrate 11 in thecontact plug 19B′ may be larger than the depth of the portionpenetrating the inter-layer insulation layer 15. The contact plug 19B′may be buried in the substrate 11.

The side wall of the contact plug 19B′ may abut the trench 31. Thetrenches 31 may be self-aligned with the side walls of the contact plug19B′. The trenches 31 may be self-aligned with the exposed side walls ofthe contact plug 19B′. From a top view, the contact plug 19B′ may beshaped as an oval or circle broken between two facing surfaces. Thewidth WT′ of the top portion of the contact plug 19B′ may be larger thanthe width WB′ of the bottom portion. A cross section of the contact plug19B′ may have a sloped shape. The exposed side wall of the contact plug19B′ may include a straight profile. The non-exposed side wall of thecontact plug 19B′ may include a round profile.

As the trench 31 is formed, a portion of the preliminary spacer 18A maybe removed (R′). As the preliminary spacer 18A is etched, the plugspacer 18′ may be formed. The plug spacer 18′ may be formed as thepreliminary spacer 18A is cut. The plug spacer 18′ may cover thenon-exposed side wall of the contact plug 19B′. The plug spacer 18′ mayinclude a shape surrounding the outer wall of the contact plug 19B′. Theplug spacer 18′ may not overlap the trench 31.

The top view of the plug spacer 18′ may have a discontinuous ring shape.The top view of the plug spacer 18′ may be shaped as curved or roundshapes facing each other. The top view of the lower cross section of theplug spacer 18′ may have a ring shape. The circumference of the plugspacer 18′ may reduce from the top portion to the bottom portion. Across section of the plug spacer 18′ may have a sloped shape. The plugspacer 18′ may have a continuous ring shape and a continuous ring shapefrom the top portion to the bottom portion. The plug spacer 18′ may bepositioned between trenches 31. The plug spacer 18′ may not overlap thetrenches 31.

The plug spacer 18′ positioned on the lower outer wall of the contactplug 19B′ may be referred to as a bottom spacer RS. The plug spacer 18′may include the bottom spacer RS. The bottom spacer RS may be positionedon the lower outer wall of the contact plug 19B′. The bottom spacer RSmay be formed in an area which is narrower than the width WT′ of the topportion of the contact plug 19B′ and is wider than the width WB′ of thebottom portion. The bottom spacer RS may be formed between the contactplug 19B′ and the trench 31. The bottom spacer RS may be formed betweenthe bottom edge of the contact plug 19B′ and the trench 31. The bottomspacer RS may be connected with the plug spacer 18′. The bottom spacerRS may have a shape surrounding the lower outer wall of the contact plug19B′. From a top view, the bottom spacer RS may have a ring shape.

Referring to FIG. 4B, a preliminary gate insulation layer 32A may beformed on and may directly contact the bottom surface and side walls ofthe trench 31. The top view of FIG. 4B may be identical to that of FIG.2H. The preliminary gate insulation layer 32A may be formed on and maydirectly contact the exposed side wall of the contact plug 19B′. Thepreliminary gate insulation layer 32A may be formed on and may directlycontact the surface of the trench 31. Before forming the preliminarygate insulation layer 32A, etch damage to the surface of the trench 31may be cured. For example, a sacrificial oxide may be formed by thermaloxidation and may then be removed.

The preliminary gate insulation layer 32A may be formed by depositing anoxide film. The preliminary gate insulation layer 32A may be formed onand may directly contact the bottom surface and side wall of the trench31. The preliminary gate insulation layer 32A may be formed on and maydirectly contact the side wall of the inter-layer insulation layer 15,exposed by the trench 31. The preliminary gate insulation layer 32A maybe formed on and may directly contact the side wall of the contact plug19B′, exposed by the trench 31. The preliminary gate insulation layer32A may be formed on and may directly contact the side wall of thebottom spacer RS, exposed by the trench 31. The preliminary gateinsulation layer 32A may be formed on and may directly contact the topsurface and side wall of the trench hard mask 30 exposed by the trench31. Accordingly, the preliminary gate insulation layer 32A may cover thetrench 31, inter-layer insulation layer 15, bottom spacer RS, contactplug 19B′, and trench hard mask 30. The preliminary gate insulationlayer 32A may be formed by a deposition method, such as chemical vapordeposition (CVD) or atomic layer deposition (ALD).

According to an embodiment, the preliminary gate insulation layer 32Amay be formed by oxidation. The preliminary gate insulation layer 32Amay be formed by thermal oxidation. According to an embodiment, thepreliminary gate insulation layer 32A may be formed by oxidating thebottom surface and side walls of the trench 31. According to anembodiment, the preliminary gate insulation layer 32A may be formed byoxidating the bottom surface and side walls of the trench 31. Thepreliminary gate insulation layer 32A may be formed by oxidating theexposed side walls of the contact plug 19B′. The preliminary gateinsulation layer 32A may be formed by oxidating the side wall of theinter-layer insulation layer 15, exposed by the trench 31. Thepreliminary gate insulation layer 32A may be formed by oxidating thecontact plug 19B′ exposed by the trench 31. The preliminary gateinsulation layer 32A may be formed by oxidating the side wall of thebottom spacer RS exposed by the trench 31. The oxide film formed on thetop surface and the side wall of the trench hard mask 30, exposed by thetrench 31, may be smaller in thickness than the oxide film formed on theside wall of the inter-layer insulation layer 15. No oxide film may beformed on the top surface and side wall of the trench hard mask 30exposed by the trench 31. Accordingly, the preliminary gate insulationlayer 32A may cover the trench 31, the side wall of the inter-layerinsulation layer 15, and the side wall of the contact plug 19B′.

The preliminary gate insulation layer 32A may include, for example,silicon oxide, silicon nitride, silicon oxynitride, a high-k material,or a combination thereof. The high-k material may include a materialhaving a larger dielectric constant than the dielectric constant ofsilicon oxide. The high-k material may include a hafnium-containingmaterial. The hafnium-containing material may include hafnium oxide,hafnium silicon oxide, hafnium silicon oxynitride, or a combinationthereof. According to an embodiment, the high-k material may includelanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconiumsilicon oxide, zirconium silicon oxynitride, aluminum oxide, or acombination thereof. As the high-k material, other known high-kmaterials may be optionally used.

Referring to FIG. 4C, a gate electrode 33 may be formed on and maydirectly contact the preliminary gate insulation layer 32A. The top viewof FIG. 4C may be the same as FIG. 2J. To form the gate electrode 33, aconductive layer (not shown) may be formed to fill the trench 31, andthen, a recessing process may be performed. As the recessing process, anetchback process may be performed, or a chemical mechanical polishing(CMP) process and an etchback process may sequentially be performed. Thegate electrode 33 may have a recessed shape meaning that it is onlypartially filling the trench 31. The top surface of the gate electrode33 may be at a lower level than the bottom surface of the contact plug19B′.

The gate electrode 33 may include a metal, metal nitride, or acombination thereof. For example, the gate electrode 33 may be formed oftitanium nitride (TiN), tungsten (W), or titanium nitride/tungsten(TiN/W). The titanium nitride/tungsten (TiN/W) may have a structurewhich results from conformally forming titanium nitride and thenpartially filling the trench 31 with tungsten. As the gate electrode 33,titanium nitride alone may be used, which may be referred to as a “TiNOnly” structure of gate electrode 33. The gate electrode 33 may includea tungsten-containing material that includes tungsten as a main element.

Subsequently, a doping process may be optionally performed. The dopingprocess may include, e.g., implantation or plasma doping (PLAD).

A preliminary gate capping layer 34A may be formed on and may directlycontact the gate electrode 33. The remainder of the trench 31 above thegate electrode 33 may be filled with the preliminary gate capping layer34A. The preliminary gate capping layer 34A may cover the preliminarygate insulation layer 32A and the gate electrode 33. The preliminarygate capping layer 34A includes an insulation material. The preliminarygate capping layer 34A may include, for example, silicon nitride.According to an embodiment, the preliminary gate capping layer 34A mayinclude, for example, silicon oxide. The preliminary gate capping layer34A may have a multi-layer structure. The preliminary gate capping layer34A may include one or more layers. The preliminary gate capping layer34A may have a multi-layer nitride-oxide-nitride (NON) structure.

Referring to FIG. 4D, a gate capping layer 34 may be formed in thetrench 31. The top view of FIG. 4D may be the same as FIG. 2K. The topsurface of the gate capping layer 34 may be at the same level as the topsurface of the inter-layer insulation layer 15. To that end, chemicalmechanical polishing (CMP) may be performed upon forming the gatecapping layer 34. The gate capping layer 34 may be formed via an etchingprocess using a separate mask. During this course, the trench hard mask30, preliminary gate insulation layer 32A, and preliminary gate cappinglayer 34A, positioned on the top surface of the contact plug 19B′ andthe inter-layer insulation layer 15 may be removed. Accordingly, the topsurface of the inter-layer insulation layer 15 may be exposed.

As a portion of the preliminary gate insulation layer 32A is removed, agate insulation layer 32 may be formed inside the trench 31. The gateinsulation layer 32, the gate electrode 33, and the gate capping layer34 may form a gate structure 35. The gate structure 35 may be formed inthe trench 31. The gate structure 35 may extend in a line shape. Thegate structure 35 may be referred to as a ‘buried gate structure.’

The gate insulation layer 32 may be formed on and may directly contactthe surface of the trench 31 and the side wall of the inter-layerinsulation layer 15. The gate insulation layer 32 may be formed on andmay directly contact the side wall of the contact plug 19B′. The gateinsulation layer 32 may be formed between the contact plug 19B′ and thegate capping layer 34.

Referring to FIG. 4E, the plug spacer 18′ may include a curved or roundouter wall 18′R. The curved or round outer wall 18′R may include acurved or round shape. The plug spacer 18′ may include parallel cutsurfaces 18′C. The curved or round outer wall 18′R and the parallel cutsurfaces 18′C may be continuous. The top view of the curved or roundouter wall 18′R may form symmetry.

The top view of the cross section in the D1 direction of the plug spacer18′ at a higher level may have a discontinuous ring shape. The top viewof the cross section in the D1 direction of the plug spacer 18′ at ahigher level may have round shapes facing each other. The circumferenceof the plug spacer 18′ may decrease from the higher level to the lowerlevel. Accordingly, a cross section in the D2 direction of the plugspacer 18′ may have a sloped shape. The top view of the cross section inthe D1 direction of the plug spacer 18′ at a higher level may have aring shape.

The plug spacer 18′ may include the bottom spacer RS. The bottom spacerRS may be connected with the plug spacer 18′. The bottom spacer RS maybe positioned at a lower level of the plug spacer 18′. The bottom spacerRS may partially include parallel cut surfaces and have a continuousshape. The circumference of the bottom spacer RS may decrease from thehigher level to the lower level. The bottom spacer RS may include a ringshape whose circumference decreases from the higher level to the lowerlevel. The bottom spacer RS at the higher level may be thinned by thecut surfaces. Thus, the thickness of the bottom spacer RS may increasefrom the higher level to the lower level. The thickness of the bottomspacer RS at the lower level may be identical to the thickness of theplug spacer 18′.

According to the above-described embodiment, the process difficulty informing the contact plug 19B′ may be reduced by forming the contact plug19B′ earlier than the gate electrode 33. Further, a short defect betweenthe contact plug 19B′ and the gate electrode 33 may be mitigated byforming the gate insulation layer 32 on the side wall of the contactplug 19B′. The short defect between the contact plug 19B′ and the gateelectrode 33 may be further mitigated by forming the bottom spacer RS onthe lower outer wall of the contact plug 19B′.

FIG. 5 is a cross-sectional view illustrating a top view of asemiconductor device 300 according to an embodiment of the presentdisclosure.

The semiconductor device 300 may include a plurality of memory cells.Each memory cell may include an active area 104, an element isolationlayer (not shown), a gate structure BG, a bit line contact plug BLC, abit line structure BL, and a memory element 125. Each memory cell mayinclude a first trench TC1 and a second trench TC2 formed in thesubstrate and spaced apart from each other. The first trench TC1 may befilled with a first gate structure BG1. The second trench TC2 may befilled with a second gate structure BG2. The gate structure BG mayextend in a first direction X, and the bit line structure BL may extendin a second direction Y. The first direction X may cross the seconddirection Y.

Each gate structure BG may include a gate insulation layer GP, a gateelectrode GE, and a gate capping layer (not shown). The gate structureBG may correspond to the gate structure BG of FIG. 1A. The gateinsulation layer GP may correspond to the gate insulation layer 107 ofFIG. 1A. The gate structure BG may be referred to as a ‘buried gatestructure.’

Each bit line structure BL may include a bit line hard mask (not shown),a bit line 111, and a barrier layer (not shown). Bit line spacers 115may be formed on both side walls of the bit line structure BL. The bitline contact plug BLC may be formed under the bit line structure BL.Each memory cell may include a storage node contact plug (not shown), amemory element 125, and a landing pad 120. The storage node contact plug(not shown) may be formed under the memory element 125. The storage nodecontact plug (not shown) may neighbor the bit line contact plug BLC. Thestorage node contact plug (not shown) may be formed spaced apart fromthe gate electrode GE. The landing pad 120 may overlap the storage nodecontact plug (not shown) and the bit line 111.

One side wall of the bit line contact plug BLC may be self-aligned withthe gate structure BG. The bit line contact plug BLC may be shaped as arectangular pillar. The bit line contact plug BLC may include a firstside surface contacting the first gate structure BG1 and a second sidesurface contacting the second gate structure BG2. The first side surfacemay contact the first gate insulation layer included in the first gatestructure BG1, and the second side surface may contact the second gateinsulation layer included in the second gate structure BG2. The firstside surface and the second side surface may be parallel with eachother. The first side surface and the second side surface may have avertical shape. The first side surface and the second side surface mayhave a sloped shape.

FIGS. 6A to 61 are cross-sectional views illustrating a method formanufacturing a semiconductor device according to an embodiment of thepresent disclosure. FIGS. 6A to 61 are cross-sectional views taken alongline B-B′ of FIG. 5. First, by the method illustrated in FIGS. 3A to 31,the source/drain area SD, contact plug 19B, plug spacer 18, inter-layerinsulation layer 15, gate electrode (not shown), gate insulation layer(not shown), and gate capping layer (not shown) may be formed. In FIGS.6A to 61, the same reference numbers are used to denote the sameelements as those in FIGS. 3A to 31. Detailed description of duplicateelements may be omitted.

Referring to FIG. 6A, a barrier metal layer 110A may be formed on andmay directly contact the inter-layer insulation layer 15 and the contactplug 19B. The height of the barrier metal layer 110A may be smaller thanthe height of the inter-layer insulation layer 15. The barrier metallayer 110A may include titanium nitride (TiN), tantalum nitride (TaN),tungsten nitride (WN), or a combination thereof. According to anembodiment, the barrier metal layer 110A may include a titanium nitride(TiN)-containing material.

The bit line layer 111A may be formed on and may contact the barriermetal layer 110A. The bit line layer 111A may be formed of a materialhaving a lower resistivity than the contact plug 19B. The bit line layer111A may include a metal material having a lower resistivity than thecontact plug 19B. For example, the bit line layer 111A may includemetal, metal nitride, metal silicide, or a combination thereof. The bitline layer 111A may include a tungsten-containing material that hastungsten as a main element. For example, the bit line layer 111A may beformed by stacking tungsten silicide, tungsten nitride film, and atungsten film. According to an embodiment, the bit line layer 111A mayinclude tungsten W or a tungsten compound.

The bit line hard mask layer 112A may be formed on and may directlycontact the bit line layer 111A. The bit line hard mask layer 112A maybe formed of an insulation material. The bit line hard mask layer 112Amay be formed of a material having an etch selectivity to the bit linelayer 111A. The bit line hard mask layer 112A may include, for example,silicon oxide, silicon nitride, silicon oxynitride, or a combinationthereof. According to an embodiment, the bit line hard mask layer 112Amay be formed of silicon nitride.

A bit line mask 113 may be formed on and may contact the bit line hardmask layer 112A. The bit line mask 113 may include a photoresistpattern. The bit line mask 113 may have a line shape extending in anyone direction. The line width of the bit line mask 113 may be smallerthan the diameter of the top surface of the contact plug 19B.

Referring to FIG. 6B, the bit line structure BL may be formed. The bitline structure BL may include a bit line contact plug 19, a barrierlayer 110, a bit line 111, and a bit line hard mask 112.

The bit line hard mask layer 112A may be etched using the bit line mask113 as an etch mask. Thus, the bit line hard mask 112 may be formed. Thebit line layer 111A, barrier metal layer 110A, and contact plug 19B maybe etched using the bit line hard mask 112 as an etch mask. Thus, thebit line 111, barrier layer 110, and bit line contact plug 19 may beformed. The bit line contact plug 19, barrier layer 110, bit line 111,and bit line hard mask 112 may have the same line width. The bit line111 may extend in any one direction while covering the barrier layer110. The bit line 111 may extend in a line shape.

As the contact plug 19B is etched, the bit line contact plug 19 may beformed on and may contact the source/drain area SD. As the contact plug19B is etched, the plug spacer 18 may be removed. A gap 114 may beformed in a portion of the contact plug 19B and the space where the plugspacer 18 has been removed. Gaps 114 may be formed on both side walls ofthe bit line contact plug 19. The gaps 114 may be independently formedon both the side walls of the bit line contact plug 19. The pair of gaps114 may be separated by the bit line contact plug 19. The bit linecontact plug 19 may interconnect the source/drain area SD and the bitline 111. The diameter of the bit line contact plug 19 may be smallerthan the diameter of the contact plug 19B.

Referring to FIG. 6C, bit line spacers 115 may be formed on both of theside walls of the bit line contact plug 19 and both of the side walls ofthe bit line structure BL. The bit line spacer 115 may have a pillarshape filling the gap 114. The bit line spacer 115 may prevent anymaterial from filling the gap 114 in a subsequent process. The bit linespacers 115 may be independently formed on both sides of the bit linecontact plug 19. The bit line spacer 115 may extend in a line shape. Thetop surface of the bit line spacer 115 may be at the same level as thetop surface of the bit line structure BL.

The bit line spacer 115 may include an insulation material. The bit linespacer 115 may include a low-k material. The bit line spacer 115 mayinclude oxide or nitride. The bit line spacer 115 may include, forexample, silicon oxide, silicon nitride, or metal oxide. The bit linespacer 115 may include SiO₂, Si₃N₄, or SiN. The bit line spacer 115 mayinclude a multi-layer spacer. The bit line spacer 115 may include an airgap (not shown). Thus, a pair of line-type air gaps may be formed onboth side walls of the bit line spacer 115. The pair of line-type airgaps may be symmetrical with each other. According to an embodiment, themulti-layer spacer may include a first spacer, a second spacer, and athird spacer, and the third spacer may be positioned between the firstspacer and the second spacer. The multi-layer spacer may include an NONstructure in which an oxide spacer is positioned between nitridespacers. According to an embodiment, the multi-layer spacer may includea first spacer, a second spacer, and an air gap between the first spacerand the second spacer.

According to an embodiment, the gap 114 may be filled not with the bitline spacer 115 but with a bit line contact insulation layer (notshown). The top surface of the bit line contact insulation layer (notshown) may be at the same level as the top surface of the bit linecontact plug 19. The bit line spacer 115 may be formed on and maycontact the bit line contact insulation layer (not shown). The bit linecontact insulation layer (not shown) may include an insulation material.

Referring to FIG. 6D, a bit line inter-layer insulation layer (notshown) may be formed to fill the space between the bit line structuresBL. The bit line inter-layer insulation layer (not shown) may beplanarized to expose the top of the bit line structure BL. The bit lineinter-layer insulation layer (not shown) may extend parallel with thebit line structure BL.

The bit line inter-layer insulation layer (not shown) may be formed of amaterial having an etch selectivity to the bit line spacer 115. The bitline inter-layer insulation layer (not shown) may include an insulationmaterial. The bit line inter-layer insulation layer (not shown) mayinclude oxide or nitride. The bit line inter-layer insulation layer (notshown) may include, for example, silicon oxide, silicon nitride, ormetal oxide. The bit line inter-layer insulation layer (not shown) mayinclude SiO₂, Si₃N₄, or SiN. The bit line inter-layer insulation layer(not shown) may include a spin-on insulation material (e.g., spin-ondielectric (SOD)).

Subsequently, a storage node contact opening H may be formed in the bitline inter-layer insulation layer (not shown). The storage node contactopening H may be formed by etching the bit line inter-layer insulationlayer (not shown) using a storage node contact opening mask (not shown)as an etch mask. The storage node contact opening H may be formed spacedapart from the bit line contact plug 19. The storage node contactopening mask (not shown) may include a photoresist pattern.

The storage node contact opening H may be formed between bit linestructures BL. The bottom surface of the storage node contact opening Hmay extend to the inside of the substrate 11. The element isolationlayer 13, inter-layer insulation layer 15, and source/drain area SD maybe recessed to a predetermined depth while forming the storage nodecontact opening H. A portion of the substrate 11 may be exposed by thestorage node contact opening H. The bottom surface of the storage nodecontact opening H may be positioned at a lower level than the topsurface of the substrate 11. The bottom surface of the storage nodecontact opening H may be at a higher level than the bottom surface ofthe bit line contact plug 19. The bottom surface of the storage nodecontact opening H may be at the same level as the bottom surface of thebit line contact plug 19. A dip-out and trimming process may beperformed to form the storage node contact opening H. The storage nodecontact opening H may be formed without loss in the bit line spacer 115by the deep-out process. The area of the side surface and bottom of thestorage node contact opening H may be increased by the trimming process.Part of the inter-layer insulation layer 15 and the substrate 11 may beremoved by the trimming process. The inter-layer insulation layer 15 maybe etched by dry etching. According to an embodiment, the inter-layerinsulation layer 15 may be etched by isotropic etching. Accordingly, thesource/drain area SD may be exposed through the storage node contactopening H. A lower portion of the storage node contact opening H mayextend laterally, forming a bulb shape.

Referring to FIG. 6E, a storage node contact plug SNC may be formed inthe storage node contact opening H. The storage node contact plug SNCmay include a lower plug 116, an ohmic contact layer 117, a conductiveliner 118, and an upper plug 119. The storage node contact plug SNC maybe formed spaced apart from the bit line contact plug 19.

First, the lower plug 116 may be formed in the storage node contactopening H. To form the lower plug 116, polysilicon may be deposited tofill the storage node contact opening H, and a planarization process andan etchback process may then be performed sequentially. The bit linespacer 115 may be positioned between the bit line 111 and the lower plug116. The bit line spacer 115 may be positioned between the bit linecontact plug 19 and the lower plug 116. The bottom surface of the lowerplug 116 may connect to the source/drain area SD. The top surface of thelower plug 116 may be positioned at a lower level than the top surfaceof the bit line 111. The lower plug 116 may include a silicon-containingmaterial. The lower plug 116 may be doped with an impurity. For example,impurity doping may be performed by a doping process, e.g.,implantation. According to an embodiment, the lower plug 116 mayinclude, for example, polysilicon.

The ohmic contact layer 117 may be formed on and may contact the lowerplug 116. To form the ohmic contact layer 117, deposition and annealingof a silicidable metal layer may be performed. The ohmic contact layer117 may include metal silicide. The ohmic contact layer 117 may includecobalt silicide (CoSi_(x)). According to an embodiment, the ohmiccontact layer 117 may include CoSi₂. Thus, it is possible to formlow-resistance cobalt silicide while enhancing contact resistance.

The conductive liner 118 may be formed on and may directly contact thetop surface of the ohmic contact layer 117 and some side surface portionof the bit line spacer 115. The conductive liner 118 may be omitted. Theconductive liner 118 may include metal or metal nitride. The conductiveliner 118 may include titanium (Ti), titanium nitride (TiN), titaniumsilicon nitride (TiSiN), tantalum (Ta), tantalum nitride (TaN), tungstennitride (WN), or a combination thereof. According to an embodiment, theconductive liner 118 may include titanium nitride.

The upper plug 119 may be formed on and may contact the conductive liner118. The upper plug 119 may fill the rest of the storage node contactopening H. The upper plug 119 may be formed, for example, by chemicalvapor deposition (CVD), physical vapor deposition (PVD), or atomic layerdeposition (ALD). To increase the deposition effect, the upper plug 119may use a plasma. For example, the upper plug 119 may be formed by,e.g., plasma enhanced CVD (PECVD) or plasma enhanced ALD (PEALD).According to an embodiment, the upper plug 119 may be formed, forexample, by chemical vapor deposition (CVD). The upper plug 119 may beplanarized to expose the top surface of the bit line structure BL.Accordingly, the top surface of the upper plug 119 and the top surfaceof the bit line structure BL may be at the same level.

The upper plug 119 may include a metal-containing material. The upperplug 119 may include a conductive material. The upper plug 119 mayinclude one or more of gold (Au), silver (Ag), copper (Cu), aluminum(Al), nickel (Ni), tungsten (W), titanium (Ti), platinum (Pt), palladium(Pd), Tin (Sn), lead (Pb), zinc (Zn), indium (In), cadmium (Cd),chromium (Cr), and molybdenum (Mo). According to an embodiment, theupper plug 119 may include a tungsten (W)-containing material. The upperplug 119 may include tungsten (W).

Referring to FIG. 6F, a landing pad layer 120A may be formed on and maydirectly contact the upper plug 119, bit line spacer 115, and bit linehard mask 112. The landing pad layer 120A may include a metal-containingmaterial. The landing pad layer 120A may be formed of a single film or amulti-layer film. The landing pad layer 120A may include a conductivematerial. The landing pad layer 120A may include a metal-containingmaterial. The landing pad layer 120A may include one or more of gold(Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), tungsten(W), titanium (Ti), platinum (Pt), palladium (Pd), Tin (Sn), lead (Pb),zinc (Zn), indium (In), cadmium (Cd), chromium (Cr), and molybdenum(Mo). According to an embodiment, the landing pad layer 120A may includea tungsten (W)-containing material. The landing pad layer 120A mayinclude tungsten (W), PVD-W, or a tungsten compound.

A landing pad hard mask layer 121A and a landing pad mask 122 maysequentially be formed on the landing pad layer 120A. The landing padhard mask layer 121A may include an insulation material. The landing padmask 122 may include a photoresist pattern. The landing pad mask 122 mayhave a line shape extending in any one direction.

Referring to FIG. 6G, the landing pad hard mask 121 may be formed byetching the landing pad hard mask layer 121A using the landing pad mask122 as an etch mask. A landing pad 120 may be formed by etching thelanding pad layer 120A using the landing pad hard mask 121 as an etchmask. The landing pad 120 may partially overlap the bit line structureBL. The landing pad 120 may be electrically connected with the upperplug 119. A landing pad hole LH may be formed in the upper plug 119. Theshape of the landing pad hole LH may not be constant. The bottom surfaceof the landing pad hole LH may be at a higher level than the bottomsurface of the bit line hard mask 112. The top of the bit line spacer115 and the upper plug 119 may be exposed by etching a portion of theupper plug 119 using the landing pad hard mask 121 as an etch mask.

Subsequently, a capping layer 123A may be formed on and may directlycontact the upper plug 119 and the landing pad 120. The capping layer123A may cover the landing pad 120, landing pad hard mask 121, bit linespacer 115, bit line hard mask 112, and upper plug 119. The cappinglayer 123A may fill the landing pad hole LH. The height of the cappinglayer 123A may be larger than the sum of the height of the landing pad120 and the height of the landing pad hard mask 121.

The capping layer 123A may include a poor step-coverage material. Forexample, the capping layer 123A may be formed using plasma chemicalvapor deposition (PECVD). The capping layer 123A may include aninsulation material. The capping layer 123A may include oxide ornitride. The capping layer 123A may include, for example, silicon oxideor silicon nitride. The capping layer 123A may include, for example,silicon nitride.

Referring to FIG. 6H, the capping layer 123A may be etched using acapping mask (not shown) as an etch mask. Thus, a cell capping layer 123may be formed. As the capping layer 123A is etched, the top surface ofthe landing pad 120 may be partially etched. The top surface level ofthe cell capping layer 123 may be identical to the top surface level ofthe landing pad 120.

The cell capping layer 123 may fill the space between the upper plug 119and the landing pad 120. The cell capping layer 123 may cover the top ofthe bit line spacer 115. The cell capping layer 123 may be planarized toexpose the top surface of the landing pad 120. The cell capping layer123 may extend parallel with the landing pad 120. The cell capping layer123 may play a role to protect the landing pad 120 from the subsequentprocess.

Referring to FIG. 6I, an etch stop layer 124 may be formed on and maycontact the landing pad 120 and the cell capping layer 123. A memoryelement 125 may be formed on and may contact the landing pad 120 toelectrically connect to the landing pad 120. The memory element 125 maybe implemented in various shapes. The memory element 125 may be acapacitor. Thus, the memory element 125 may include a storage nodecontacting the landing pad 120.

The storage node may be shaped as a cylinder or a pillar. A capacitordielectric layer may be formed on and may contact the surface of thestorage node. The capacitor dielectric layer may include at least oneselected from zirconium oxide, aluminum oxide, or hafnium oxide. Forexample, the capacitor dielectric layer may have a ZAZ structure inwhich a first zirconium oxide, an aluminum oxide, and a second zirconiumoxide are stacked one over another. A plate node is formed on thecapacitor dielectric layer. The storage node and the plate node mayinclude a metal-containing material. The memory element 125 may includea variable resistor. The variable resistor may include a phase changematerial. According to an embodiment, the variable resistor may includetransition metal oxide. According to an embodiment, the variableresistor may be a magnetic tunnel junction (MTJ).

FIG. 7 is a cross-sectional view illustrating a semiconductor device300, taken along line A-A′ of FIG. 5 for the steps of FIG. 6I. In FIG.7, the same reference numbers are used to denote the same elements asthose in FIGS. 6A to 6I. Detailed description of duplicate elements maybe omitted.

Referring to FIG. 7, a bit line structure BL may be positioned on thebit line contact plug 19 and the inter-layer insulation layer 15. Thebit line structure BL may include a bit line contact plug 19, a barrierlayer 110, a bit line 111, and a bit line hard mask 112. A cell cappinglayer 123 may be formed on and may directly contact the bit linestructure BL.

Trenches 21 may be positioned on both side walls of the bit line contactplug 19. The trenches 21 may be positioned in the substrate 11 and bealigned with both of the side walls of the bit line contact plug 19. Thegate insulation layer 22, gate electrode 23, and gate capping layer 24may be positioned inside the trench 21.

The gate insulation layer 22 may be positioned directly on the surfaceof the trench 21 and the side wall of the bit line contact plug 19. Thegate insulation layer 22 may be positioned between the gate cappinglayer 24 and the bit line contact plug 19. The gate insulation layer 22may have a shape vertically extending from the bottom surface of thetrench 21.

The gate electrode 23 may be formed on and may directly contact the gateinsulation layer 22. The gate electrode 23 may have a recessed shapemeaning that it is only partially filling the trench 21. The top surfaceof the gate electrode 23 may be at a lower level than the bottom surfaceof the bit line contact plug 19. The top surface of the gate electrode23 may be at a lower level than the top surface of the active area 14.The rest of the trench 21 on the gate electrode 23 may be filled withthe gate capping layer 24. The top surface of the gate capping layer 24may be at the same level as the top surface of the inter-layerinsulation layer 15.

The width 19WT of the top portion of the bit line contact plug 19 may beidentical to the width 19WB of the bottom portion. The bit line contactplug 19 may neighbor the gate electrode 23 and the gate capping layer24, with the gate insulation layer 22 interposed therebetween. The bitline contact plug 19 may directly contact the gate insulation layer 22.A side wall of the bit line contact plug 19 may be self-aligned with thegate insulation layer 22. The bit line contact plug 19 may be shaped asa rectangular pillar. The bit line contact plug 19 may correspond to thebit line contact plug BLC of FIG. 5. The bottom surface of the bit linecontact plug may be curved as shown in FIG. 7, however, the bit linecontact plug is not limited to this configuration.

A short defect between the bit line contact plug 19 and the gateelectrode 23 may be mitigated by the gate insulation layer 22.Accordingly, the characteristics of the semiconductor device may beenhanced.

FIG. 8 is a cross-sectional view illustrating a semiconductor device 400according to an embodiment of the present disclosure. FIG. 8 is across-sectional view taken along line A-A′ of FIG. 5. The semiconductordevice 400 of FIG. 8 may be similar to the semiconductor device 300 ofFIG. 7. In FIG. 8, the same reference numbers are used to denote thesame elements as those in FIGS. 4A to 4D and FIGS. 6A to 61. Detaileddescription of duplicate elements may be omitted.

First, the gate insulation layer 32, gate electrode 33, and gate cappinglayer 34 may be formed in the trench 31 by the method described above inconnection with FIGS. 4A to 4D. Subsequently, the bit line structure BL,storage node contact (not shown), landing pad (not shown), and memoryelement (not shown) may be formed by the method described above inconnection with FIGS. 6A to 6I. The bit line structure BL may include abit line contact plug 19′, a barrier layer 110, a bit line 111, and abit line hard mask 112. A cell capping layer 123 may be formed on andmay contact the bit line structure BL.

Referring to FIG. 8, a bit line structure BL may be positioned on thebit line contact plug 19′ and the inter-layer insulation layer 15.Trenches 31 may be positioned on both side walls of the bit line contactplug 19′. The gate insulation layer 32, gate electrode 33, and gatecapping layer 34 may be positioned inside the trench 31.

The gate insulation layer 32 may be formed on and may directly contactthe surface of the trench 31 and the side wall of the bit line contactplug 19′. The gate insulation layer 32 may have a shape verticallyextending from the bottom surface of the trench 31. The gate insulationlayer 32 may be positioned between the gate capping layer 34 and the bitline contact plug 19′.

The gate electrode 33 may be formed on and may directly contact the gateinsulation layer 32. The gate electrode 33 may have a recessed shapemeaning that it is only partially filling the trench 31. The top surfaceof the gate electrode 33 may be at a lower level than the bottom surfaceof the bit line contact plug 19′. The top surface of the gate electrode33 may be at a lower level than the top surface of the active area 14.The remainder of the trench 31 above the gate electrode 33 may be filledwith the gate capping layer 34. The top surface of the gate cappinglayer 34 may be at the same level as the top surface of the inter-layerinsulation layer 15.

The width 19WT′ of the top portion of the bit line contact plug 19′ maybe larger than the width 19WB′ of the bottom portion. The bottom spacerRS may be positioned on the lower outer wall of the bit line contactplug 19′. The bottom spacer RS may be positioned on the outer wall ofthe bit line contact plug 19′ in the area which is narrower than thewidth 19WT′ of the top portion of the bit line contact plug 19′ and iswider than the width 19WB′ of the bottom portion. The bottom spacer RSmay be positioned between the trench 31 and the bottom edge of the bitline contact plug 19′. The bottom spacer RS may have a shape surroundingthe lower outer wall of the bit line contact plug 19′. From a top view,the bottom spacer RS may have a ring shape. The thickness of the bottomspacer RS may increase from the higher level to the lower level. Thebottom surface of the bottom spacer RS may be positioned at a higherlevel than the bottom surface of the bit line contact plug 19′.

The bit line contact plug 19′ may neighbor the gate electrode 33 and thegate capping layer 34, with the gate insulation layer 32 interposedtherebetween. The bit line contact plug 19′ may directly contact thegate insulation layer 32. A side wall of the bit line contact plug 19′may be self-aligned with the gate insulation layer 32. The bit linecontact plug 19′ may directly contact the bottom spacer RS. The bit linecontact plug 19′ may neighbor the gate insulation layer 32, with thebottom spacer RS interposed therebetween.

A short defect between the bit line contact plug 19′ and the gateelectrode 33 may be mitigated by the gate insulation layer 32. Since thebottom spacer RS is formed on the lower outer wall of the bit linecontact plug 19′, the short defect between the bit line contact plug 19′and the gate electrode 33 may be further mitigated. Accordingly, thecharacteristics of the semiconductor device may be enhanced.

FIGS. 9A and 9B are cross-sectional views illustrating a top view of asemiconductor device according to an embodiment of the presentdisclosure. FIG. 9B is an enlarged view of portion Q of FIG. 9A. Thesemiconductor device 500 of FIGS. 9A and 9B may be similar to thesemiconductor device 300 of FIG. 5. In FIGS. 9A and 9B, the samereference numbers denote the same elements as those of FIG. 5. Detaileddescription of duplicate elements may be omitted.

Referring to FIG. 9A, the semiconductor device 500 may include aplurality of memory cells. Each memory cell may include an active area104, a gate structure BG, a bit line contact plug BLC, a plug spacer SP,a bit line structure BL, a storage node contact plug (not shown), and amemory element 125.

Each memory cell may include a first trench TC1 and a second trench TC2formed in the substrate and spaced apart from each other. The firsttrench TC1 may be filled with a first gate structure BG1. The secondtrench TC2 may be filled with a second gate structure BG2.

Each gate structure BG may include a gate insulation layer GP, a gateelectrode GE, and a gate capping layer (not shown). Each bit linestructure BL may include a bit line 111, a bit line spacer 115, and abit line contact plug BLC. Each memory cell may include a storage nodecontact plug (not shown) and a landing pad 120 on the storage nodecontact plug (not shown).

Referring to FIG. 9B, one side wall of the bit line contact plug BLC maybe self-aligned with the gate structure BG. The bit line contact plugBLC may be shaped as a rectangular pillar. The bit line contact plug BLCmay include a first side surface contacting the first gate structure BG1and a second side surface contacting the second gate structure BG2. Thefirst side surface may contact the first gate insulation layer includedin the first gate structure BG1, and the second side surface may contactthe second gate insulation layer included in the second gate structureBG2. The first side surface and the second side surface may be parallelwith each other. The first side surface and the second side surface mayhave a vertical shape. The first side surface and the second sidesurface may have a sloped shape.

A plug spacer SP may be positioned under the bit line spacer 115. Theplug spacer SP may include a pair of side walls facing each other andpositioned on both sides of the bit line contact plug BLC. The plugspacer SP may include a pair of curved or round side walls facing eachother. The plug spacer SP may be positioned in the direction crossingthe first and second gate structures BG1 and BG2. The plug spacer SP maynot overlap the first and second gate structures BG1 and BG2. The plugspacer SP may neighbor the storage node contact plug (not shown). Thethickness of the plug spacer SP may be smaller than the thickness of thebit line spacer 115. The plug spacer SP may correspond to the plugspacer SP of FIG. 1.

FIGS. 10A to 10E are cross-sectional views illustrating a method formanufacturing a semiconductor device 500 according to an embodiment ofthe present disclosure. FIGS. 10A to 10E are cross-sectional views takenalong line B-B′ of FIG. 9. The semiconductor device 500 of FIGS. 10A to10E may be similar to the semiconductor device 300 of FIGS. 6A to 61.Thus, by the method illustrated in FIGS. 3A to 3K, the source/drain areaSD, contact plug 19B, plug spacer 18, inter-layer insulation layer 15,gate electrode (not shown), gate insulation layer (not shown), and gatecapping layer (not shown) may be formed. In FIGS. 10A to 10E, the samereference numbers are used to denote the same elements as those in FIGS.3A to 3K and FIGS. 6A to 6I. Detailed description of duplicate elementsmay be omitted.

Referring to FIG. 10A, a barrier metal layer (not shown), a bit linelayer (not shown), a bit line hard mask layer (not shown), and a bitline mask (not shown) may be formed on the inter-layer insulation layer15 and the contact plug 19B. The bit line hard mask layer (not shown),the bit line layer (not shown), the barrier metal layer (not shown), andthe contact plug 19B may be etched using the bit line mask (not shown)as an etch mask. Thus, a bit line structure BL including the bit linecontact plug 19, the barrier layer 110, the bit line 111, and the bitline hard mask 112 may be formed. The bit line contact plug 19, barrierlayer 110, bit line 111, and bit line hard mask 112 may have the sameline width.

As the contact plug 19B is etched, the bit line contact plug 19 may beformed on the source/drain area SD. As the contact plug 19B is etched,the plug spacer 18 may not be removed. There may be a pair of plugspacers 18 facing each other and positioned on both sides of the bitline contact plug 19. The plug spacer 18 may not directly contact thebit line contact plug 19. The plug spacer 18 may not overlap the gateelectrode (not shown). The plug spacer 18 may not overlap the trenches(not shown). The plug spacer 18 may be formed to extend in a directionparallel with the bit line 111. The top view of the plug spacer 18 mayhave a curved or round shape. The side wall profile of the plug spacer18 may have a sloped shape. The plug spacer 18 may correspond to theplug spacer SP of FIG. 1. The plug spacer 18 may further include abottom spacer.

Gaps 114′ may be formed in spaces where a portion of the contact plug19B has been removed. Gaps 114′ may be formed on both side walls of thebit line contact plug 19. The gaps 114′ may be formed between the bitline contact plug 19 and the plug spacer 18. The gaps 114′ may beindependently formed on both the side walls of the bit line contact plug19. The pair of gaps 114′ may be separated by the bit line contact plug19. The diameter of the bit line contact plug 19 may be smaller than thediameter of the contact plug 19B.

Referring to FIG. 10B, bit line spacers 115 may be formed on both of theside walls of the bit line contact plug 19 and both of the side walls ofthe bit line structure BL. The bit line spacer 115 may have a pillarshape filling the gap 114′. According to an embodiment, the gap 114 maybe filled not with the bit line spacer 115 but with a bit line contactinsulation layer (not shown). In this case, the bit line spacer 115 maybe formed on and may contact the bit line contact insulation layer (notshown). The bit line spacer 115 may include a multi-layer spacer. Thebit line spacer 115 may include an air gap (not shown).

Subsequently, a storage node contact opening H may be formed between bitline structures BL. The bottom surface of the storage node contactopening H may extend to the inside of the substrate 11. A portion of thesubstrate 11 may be exposed by the storage node contact opening H. Alower portion of the storage node contact opening H may extendlaterally, forming a bulb shape.

Referring to FIG. 10C, a storage node contact plug SNC may be formed inthe storage node contact opening H. The storage node contact plug SNCmay include a lower plug 116, an ohmic contact layer 117, a conductiveliner 118, and an upper plug 119. The storage node contact plug SNC mayneighbor the plug spacer 18. The storage node contact plug SNC may bespaced apart from the bit line contact plug 19 and connected to thesubstrate 11. The storage node contact plug SNC may be spaced apart fromthe bit line contact plug 19 and gate electrode (not shown) andconnected to the substrate 11.

Referring to FIG. 10D, a landing pad 120 may be formed on the bit linestructure BL to partially overlap the bit line structure BL. The landingpad 120 may be electrically connected with the upper plug 119.

Subsequently, a cell capping layer 123 may be formed to cover a portionof the bit line structure BL, the side wall of the landing pad 120, andthe top surface of the upper plug 119. The cell capping layer 123 mayfill the space between the upper plug 119 and the landing pad 120.

An etch stop layer 124 may be formed on and may contact the landing pad120 and the cell capping layer 123. A memory element 125 may be formedon and may contact the landing pad 120 to electrically connect to thelanding pad 120. The memory element 125 may be implemented in variousshapes. The memory element 125 may be a capacitor. Thus, the memoryelement 125 may include a storage node contacting the landing pad 120.

The cross-sectional view of the semiconductor device 500, taken alongline A-A′ of FIG. 9A may be identical to that of FIG. 7.

Referring to FIG. 7, a bit line structure BL may be positioned on thebit line contact plug 19 and the inter-layer insulation layer 15. Thewidth 19WT of the top portion of the bit line contact plug 19 may beidentical to the width 19WB of the bottom portion. The bit line contactplug 19 may directly contact the gate insulation layer 22. A side wallof the bit line contact plug 19 may be self-aligned with the gateinsulation layer 22. The bit line contact plug 19 may be shaped as arectangular pillar. The bit line contact plug 19 may correspond to thebit line contact plug BLC of FIG. 9A.

A short defect between the bit line contact plug 19 and the gateelectrode 23 may be mitigated by the gate insulation layer 22. Since apair of plug spacers 18 remain, which are positioned on both sides ofthe bit line contact plug 19 and facing each other, a short defect dueto the bit line contact plug 19′ may be further mitigated. Accordingly,the characteristics of the semiconductor device may be enhanced.

The cross-sectional view of the semiconductor device, taken along lineA-A′ of FIG. 9A may be identical to that of FIG. 8. First, the gateinsulation layer 32, gate electrode 33, and gate capping layer 34 may beformed by the method described above in connection with FIGS. 4A to 4D.Subsequently, the bit line structure BL, storage node contact (notshown), landing pad (not shown), and memory element (not shown) may beformed by the method described above in connection with FIGS. 10A to10D.

The width 19WT′ of the top portion of the bit line contact plug 19′ maybe larger than the width 19WB′ of the bottom portion as shown in FIG. 8.The bottom spacer RS may have a shape surrounding the lower outer wallof the bit line contact plug 19′. From a top view, the bottom spacer RSmay have a ring shape. The thickness of the bottom spacer RS mayincrease from the higher level to the lower level.

According to an embodiment, the plug spacer (not shown) may include thebottom spacer RS. The bottom spacer RS may be connected with the plugspacer (not shown). The bit line contact plug 19′ may directly contactthe bottom spacer RS. The bit line contact plug 19′ may not directlycontact the plug spacer (not shown).

The bit line contact plug 19′ may directly contact the gate insulationlayer 32. A side wall of the bit line contact plug 19′ may beself-aligned with the gate insulation layer 32. The bit line contactplug 19′ may neighbor the gate insulation layer 32, with the bottomspacer RS interposed therebetween.

A short defect between the bit line contact plug 19′ and the gateelectrode 33 may be mitigated by the gate insulation layer 32. Since thebottom spacer RS is formed on the lower outer wall of the bit linecontact plug 19′, the short defect between the bit line contact plug 19′and the gate electrode 33 may be mitigated. Since a pair of plug spacers18 remain, which are positioned on both sides of the bit line contactplug 19 and facing each other, a short defect due to the bit linecontact plug 19′ may be further mitigated. Accordingly, thecharacteristics of the semiconductor device may be enhanced.

One of ordinary skill in the art will recognize that the variousembodiments of the present disclosure as described above are not limitedto the above-described embodiments and those shown in the drawings, butthat various changes, modifications, or alterations may be made theretowithout departing from the spirit and scope of the invention as definedin the following claims.

What is claimed is:
 1. A method for manufacturing a semiconductordevice, the method comprising: forming a contact hole in a substrate;filling the contact hole with a plug material; forming a contact plug byetching the plug material; forming a trench exposing a side wall of thecontact plug by etching the substrate to be aligned with a side wall ofthe contact plug; forming a gate insulation layer on the exposed sidewall of the contact plug and a surface of the trench; and forming a gateelectrode on the gate insulation layer, the gate electrode partiallyfilling the trench.
 2. The method of claim 1, further comprising: beforefilling the contact hole with the plug material, forming a preliminaryspacer covering the side wall of the contact hole; and further recessingthe substrate exposed in the contact hole using the preliminary spacer.3. The method of claim 2, wherein forming the trench includes forming aplug spacer covering a non-exposed side wall of the contact plug bycutting the preliminary spacer.
 4. The method of claim 3, wherein theplug spacer further includes a bottom spacer positioned between thetrench and a bottom edge of the contact plug.
 5. The method of claim 4,wherein the bottom spacer has a shape surrounding a lower outer wall ofthe contact plug.
 6. The method of claim 1, wherein forming the contactplug and forming the trench are simultaneously performed using oneline-type mask.
 7. The method of claim 1, wherein the trench includes apair of line-type trenches, and wherein the pair of line-type trenchesare self-aligned with the exposed side wall of the contact plug.
 8. Themethod of claim 1, wherein forming the contact hole includes: forming aninter-layer insulation layer on the substrate; forming an etch mask onthe inter-layer insulation layer; and etching the inter-layer insulationlayer and the substrate using the etch mask.
 9. The method of claim 1,further comprising: before forming the contact hole in the substrate,forming an element isolation layer defining an active area in thesubstrate, wherein the trench has a line shape crossing the active areaand the element isolation layer.
 10. The method of claim 1, wherein abottom surface of the trench is at a lower level than a bottom surfaceof the contact plug.
 11. The method of claim 1, wherein the gateinsulation layer is formed by oxidating the exposed side wall of thecontact plug and a surface of the trench.
 12. The method of claim 1,wherein a top portion of the contact plug is identical in width to abottom portion of the contact plug.
 13. The method of claim 1, wherein atop portion of the contact plug is larger in width than a bottom portionof the contact plug.
 14. The method of claim 1, wherein the exposed sidewall of the contact plug has a straight profile, and wherein thenon-exposed side wall of the contact plug has a curved or round profile.15. The method of claim 1, wherein the plug material includespolysilicon.
 16. The method of claim 1, wherein a top surface of thegate electrode is at a lower level than a bottom surface of the contactplug.
 17. A method for manufacturing a semiconductor device, the methodcomprising: forming a contact hole in a substrate; forming a plugmaterial filling the contact hole; forming a bit line contact plug byetching the plug material; forming a gate trench exposing a side wall ofthe bit line contact plug by etching the substrate to be self-alignedwith a side wall of the bit line contact plug; forming a buried gatestructure filling the gate trench; and forming a bit line on the bitline contact plug.
 18. The method of claim 17, wherein forming theburied gate structure includes: forming a gate insulation layer byoxidating the exposed side wall of the bit line contact plug and asurface of the gate trench; and forming a buried gate electrode on thegate insulation layer so that the buried gate electrode partially fillsthe gate trench.
 19. The method of claim 17, further comprising: beforeforming the plug material, forming a preliminary spacer covering theside wall of the contact hole; and further recessing the substrateexposed in the contact hole using the preliminary spacer, whereinforming the gate trench includes forming a plug spacer covering anon-exposed side wall of the bit line contact plug by cutting thepreliminary spacer.
 20. The method of claim 17, wherein forming thecontact hole includes: forming an inter-layer insulation layer on thesubstrate; forming an etch mask on the inter-layer insulation layer; andetching the inter-layer insulation layer and the substrate using theetch mask.